Question

Define the following terms related to D/A converter;                                  

            (i) resolution   (ii) accuracy    (iii) settling time         (iv) offset error      (v) gain error

Answer 1

(i)Resolution:- The resolution of DAC is defined as the smallest change that occurs in an analog output as a result of a change in digital input. It is also defined as the reciprocal of the number of the discrete steps in the full-scale output of the DAC. Resolution is a measure of precision, not accuracy.

(ii)Accuracy = The accuracy is defined as a full-scale error which is the maximum deviation of the DAC’s output from its expected(ideal) value, expressed as a percentage of full scale. there are two types of accuracy defined as Absolute accuracy is the maximum deviation between the actual converter output and the ideal converter output. and another one is Relative accuracy is the maximum deviation after gain and offset error have been removed

(iii)settling time:-The operating speed of a DAC is usually specified by giving its settling time, which is the time required for the DAC output to go from zero to full scale as the binary input is changed from all 0’s to all 1’s. It represents the time it takes for the output to settle within a specified band ±(1/2) LSB of its final value, after the change in digital input

(iv)Offset error:- Ideally, the output of a DAC will be zero volts when the binary input is all 0’s. In practice, however, there will be a very small output voltage for this situation; this is called offset error. In other words, we can say it is the output available when there no input

(v)Gain error:-It is defined as the difference between the ideal max output voltage and the actual max output voltage (after subtracting offset error). Changes the slope of the output, thereby creating the same percentage error for each step. Expressed in mV as a percentage of the maximum output.